Ein weiterer technologischer Ansatz ist das Verwenden von optischer Signalübertragung anstelle der typischen Elektrodenleitungen, die auf der elektrischen Signalübertragung beruhen. A further technological approach is the use of optical signal transmission instead of the typical electrode lines based on the electrical signal transmission.Durch die Verwendung dieser optischen Leitungen verhindert man das Einkoppeln der elektromagnetischen Störfelder eines MRI-Gerätes in die Elektrodenleitungen, aber das Gesamtsystem wird komplexer, da einerseits die elektrischen Signale erst in optische Signale umgewandelt werden müssen und aus den optischen Signalen am Stimulationsort an Hand der Signale die Stimulationsimpulse generiert werden müssen und andererseits am Stimulationsort gemessene Signale ebenfalles umgewandelt werden müssen. By using these optical cables to prevent the coupling of the electromagnetic interference fields of an MRI device in the electrode lines, but the overall system is more complex as the one hand, the electrical signals must be first converted into optical signals and from the optical signals at the stimulation on hand of the signals the stimulation pulses have to be generated and on the other hand, measured at the stimulation signals must be converted up case.Solche komplexeren Systeme erhöhen in der Regel auch den Energiebedarf eines Implantats. Such complex systems usually increases and the energy requirements of an implant.Ein solches System, dass auf optischer Signalleitung basiert ist in der Such a system that is based on optical signal line in theUS 2005/0090886 US 2005/0090886und der and theUS 7,450,996 US 7,450,996beschrieben. described.

Auch ist bevorzugt, dass elektrooptische Wandler auf unterschiedlichen Frequenzen emittieren, speziell bei verschieden Empfängern können mehrere Emissionsfrequenzen verwendet werden, auch um nach dem Entstehungsort der induzierten Spannungen differenzieren zu können und diesen in die Auswertung einfließen lassen zu können. It is also preferred that electro-optical converters emit at different frequencies, especially at different emission frequencies more receivers may be used also to differentiate according to the origin of the induced voltages and to be able to make this included in the evaluation.Dadurch sind auch differenzierte Reaktionen auf das Auftreten von MRT-Störungen möglich, je nachdem welche Elemente des IMD und/oder der zugehörigen Elektrodenleitungen und/oder Elektroden betroffen sind. This also differentiated response to the occurrence of MRI interference are possible, depending on which elements of the IMD and / or the associated electrode leads and / or electrodes are affected.

Ebenfalls bevorzugt ist, dass mindestens eine Elektrode vorhanden ist, die therapeutischen und/oder diagnostischen Zwecken dient, wobei die Elektrode sich außerhalb der des hermetisch verschlossen Gehäuses erstrecken kann oder sich auf der Außenfläche diese Gehäuses befinden kann oder Teil dieses Gehäuses sein kann. It is also preferred that at least one electrode is present which serves for therapeutic and / or diagnostic purposes, the electrode may extend outside of the hermetically sealed housing or can be located on the outer surface of this housing or may be part of this housing.

In einer weiteren bevorzugten Ausführungsform ist die mindestens eine Elektrode eine Verbindung zu mindestens einem, vom Implantat ausgehenden distal angeordneten Sensor und/oder mindestens einem Aktuator. In a further preferred embodiment, the at least one electrode is a connection to at least one outgoing from the implant distally located sensor and / or at least one actuator.

Auch ist bevorzugt, dass der elektrooptische Wandler ein Optokoppler ist. It is also preferred that the electro-optical transducer is an opto-coupler.

Auch wird bevorzugt, dass sich der elektrooptische Wandler innerhalb oder außerhalb oder in einer Gehäusedurchführung des hermetisch abgeschlossenen Gehäuses liegt. It is also preferable that the electro-optical converter is located inside or outside, or in a housing bushing of the hermetically sealed housing.

Ebenfalls bevorzugt ist, dass der elektrooptische Wandler nur Informationen zu den Amplituden und/oder der Einhüllende der Amplituden und/oder den Frequenzen und/oder bei mehren elektrooptischen Wandlern Phasen überträgt. It is also preferable that the electro-optical converter transmits only information about the amplitude and / or the envelope of the amplitudes and / or frequencies and / or with several electro-optical converters phases.

Des Weiteren ist bevorzugt, dass mehrere elektrische Zuleitungen zum elektrooptischen Wandler in Reihe und/oder parallel geschaltet sind. Furthermore, it is preferable that a plurality of electrical supply lines to the electro-optical transducer in series and / or in parallel.

Auch wird bevorzugt, dass der elektrooptische Wandler mit mindestens einem Schutzelement in Reihe und/oder parallel geschaltet ist. It is also preferable that the electro-optical converter is connected in parallel with at least one protective element in series and / or.Als Schutzelemente sind zum Beispiel, aber nicht ausschließlich, EMI-Kondensatoren und/oder Schutzdioden zu verstehen. As the protective elements are, for example, but not exclusively, EMI capacitors and / or understand protection diodes.

Die genannten Ausführungen ermöglichen, dass das Vorhandensein eines MRT oder anderer hochfrequenter starker elektromagnetischer Felder, z. The embodiments mentioned allow the presence of a MRI or other high frequency of strong electromagnetic fields, z.B. Patienten im Umfeld von Sendeanlagen, wie Mobilfunk Relaisstation, sicher von einem elektronischen Implantat erkannt werden kann, so dass das Implantat in einen (MRT-)sicheren Zustand umschalten kann. As patients in the area of ​​transmission equipment, such as mobile relay station can be reliably detected by an electronic implant so that the implant into a (MRI) safe mode can switch.Die Erfindung soll dabei sicherstellen, dass die durch das MRT hervorgerufene RF-Störung nicht oder nur minimal in die elektronische Schaltung des Implantates eingekoppelt werden kann. The invention is designed to ensure that caused by the MRI RF interference can only minimally or not be coupled to the electronic circuitry of the implant.

Claims (15)

An implantable medical device (IMD) with a hermetically closed housing, at least one control unit, at least one unit for identifying MRT (magnetic resonance tomography) interference fields, which is connected or can be connected at least to the control unit and at least one electrode and/or at least one antenna and/or at least one coil, characterised in that
the unit for identifying MRT interference fields contains at least one electro-optical converter, which converts induced voltages from the at least one electrode and/or the at least one antenna and/or the at least one coil into optical signals and, within the unit for identifying MRT interference fields, forwards these signals optically and in a potential-free manner to an evaluation unit of the unit for identifying MRT interference fields, and the evaluation unit triggers a switchover into an MRI-safe (magnetic-resonance-imaging-safe) state when a threshold of the optical signals and/or a predetermined periodic occurrence of the optical signals is exceeded.

The IMD according to Claim 1, characterised in that the unit for identifying MRT interference fields has at least one sensor, which converts the optical signals from the at least one electro-optical converter into electrical signals, which are used for MRT identification, wherein the signals from a plurality of electro-optical converters may also lead to a sensor.

The IMD according to one of the preceding claims, characterised in that at least one electrode is provided, which is used for therapeutic and/or diagnostic purposes, wherein the electrode may extend outside the hermetically sealed housing or may be located on the outer face of this housing or may be part of this housing.

The IMD according to Claim 3, characterised in that the at least one electrode is a connection to at least one sensor arranged distally starting from the implant and/or at least one actuator.

The IMD according to one of the preceding claims, characterised in that the electro-optical converter is an optocoupler.

The IMD according to one of the preceding claims, characterised in that the electro-optical converter is a sensor for electromagnetic fields, which is based on the optical properties, dependent on external electromagnetic fields, of a crystal.

The IMD according to one of the preceding claims, characterised in that the electro-optical converter only forwards information concerning:

- the amplitudes and/or

- envelopes of the amplitudes and/or

- the frequencies and/or

- phases, in configurations with multiple electro-optical converters.

The IMD according to Claim 7, characterised in that the unit for identifying MRT interference fields determines from the optical signal a scalar value, which represents the identified field strength and, when a presettable and/or variable threshold value is exceeded or when a presettable and/or variable threshold value range is reached, identifies an MRT field, wherein the scalar value may also be a functional or logical link formed from one or more pieces of information, such as amplitude information and/or frequency information and/or phase information, or weighted information.

The IMD according to Claim 8, characterised in that the information is weighted via a predetermined damping of the optical signals during the transmission of the optical signals, wherein additional different dampings can be implemented for different signal sources or types of information over various transmission frequencies.

The IMD according to one of the preceding claims, characterised in that a plurality of electrical supply lines to the electro-optical converter are connected in series and/or in parallel.

The IMD according to one of the preceding claims, characterised in that the electro-optical converter is connected to at least one protective element in series and/or in parallel.

The IMD according to one of the preceding claims, characterised in that the threshold value for MRT identification is a weighted function of the determined frequency of the induced voltages and/or the threshold value and/or the weighting factors is/are a function of static field strengths determined via other sensors or indicators, wherein the functional dependency may be either linear or non-linear.

The IMD according to one of the preceding claims, characterised in that the MRT-safe state switched on or triggered by the MRT interference identification unit is switched on for a predetermined or predeterminable time and, once this time has elapsed, said MRT-safe state is deactivated or a further MRT identification process is performed.

The IMD according to one of the preceding claims, characterised in that MRT identification only takes place if, at the same time as the MRT identification according to Claim 1, at least one further measurement method also signals MRT identification, wherein further methods are to be understood, inter alia but not exclusively, to be the following methods:

GMR sensors,

MagFET sensors,

Hall sensors,

the monitoring of battery voltages during capacitor charging processes,

the detection of RF fields,

the detection of magnetic gradient fields,

the detection of currents induced by electromagnetic fields,

the detection of specific vibrations or components designed as sensors for the detection of vibrations induced by Lorentz forces.

The IMD according to one of the preceding claims, characterised in that at least one of the following measures is initiated with MRT identification or by the MRT identification signal:

- change to an MRI-safe state,

- remain for a prolonged period of time in an MRI-safe state or a state that is insensitive to electromagnetic interference fields,

- synchronise electrical measurements (for example impedance measurements) with use of field strength minimum values that occur with periodic or pulsed electromagnetic fields, or synchronise a stimulation with use of said field strength minimum values, and

- emit electromagnetic pulses to signal (specifically to an MRI device) that a medical device, specifically an implant, is present in the electromagnetic field, with the possibility of also transferring information in this way, in addition to the interference, and displaying this on the screen of the MRI device.